1. Field of the Invention
The present invention relates to an imaging apparatus, imaging apparatus control method, and computer program. More particularly, the present invention relates to an imaging apparatus, imaging apparatus control method, and computer program, which perform focus control.
2. Description of the Related Art
With a great number of current imaging apparatuses nowadays such as still cameras, video cameras, and so forth, an auto-focus (AF) mechanism is implemented, which automatically focuses on a subject. For example, with focus control based on contrast measurement employed for many cameras, a focus position is determined by determining whether the contrast of imaged data obtained through a lens is high or low. That is to say, a position where the contrast intensity of an image becomes the maximum is detected while moving a focusing lens, and this position is regarded as a focus position.
Note that a range where the focusing lens is moved is referred to as a scan range, and lens driving is typically performed with a range between the near side and the infinity side as a scan range. Multiple sampling points which are contrast measurement points are set on the scan range, so as to determine a focus position.
With shooting employing auto-focus (AF), lens driving is generally performed with a range between the near side and the infinity side as a scan range, which results in a problem that it takes time to determine a focus position. That is, there is a shortcoming that a longer scan range means a longer focus driving length or amount for focusing, in turn meaning an increased number of sampling points for scanning AF, leading to more time for focal point adjustment. This is particularly marked with cases of using high-power optical systems with long focal distances.
In order to avoid such problems, configurations have been proposed wherein the entire range of the near side to the far side is not taken as the scan range, and rather only a partial section thereof is set as the scan range, i.e., the lens driving range, which is used as the focal position.
For example, Japanese Unexamined Patent Application Publication No. 9-211298, Japanese Unexamined Patent Application Publication No. 2003-262786, Japanese Unexamined Patent Application Publication No. 2003-230039, and Japanese Unexamined Patent Application Publication No. 2005-202064 disclose a configuration wherein the focusing lens driving range is divided into a near range and far range, reducing the overall time to focusing in scanning AF.
Specifically, Japanese Unexamined Patent Application Publication No. 9-211298 discloses a configuration wherein the moving region of the focusing lens is sectioned into a movable region and move-inhibited region, thereby restricting the driving range. Japanese Unexamined Patent Application Publication No. 2003-262786 discloses a configuration wherein the scan range is divided, and scanning AF is performed restricted to the one range specified by the user, for example.
Japanese Unexamined Patent Application Publication No. 2003-230039 discloses a configuration wherein a distance specifying button for restricting the photography range is provided, and the AF scan range is restricted in accordance with input form the distance specifying button. Japanese Unexamined Patent Application Publication No. 2005-202064 also discloses a configuration for restricting the scan range to reduce focusing time. Thus, multiple techniques have been disclosed regarding configurations for reducing the processing time of auto-focus (AF) by restricting the scan range.
Also, some cameras nowadays are capable of performing photography switched to an optimal photography mode in accordance with the distance to the subject. For example, there are cameras which have a macro mode suitable for photography in a near region (macro region) which is in the order of tens of centimeters to the subject, a magnifying glass mode suitable for even closer photography in a very near region (magnifying glass region) which is in the order of several centimeters to the subject, and so on. With photography in these modes, photography is performed with a focus limit set in which the focus region is set to a particular range.
With cameras having such modes, there is a technique whereby a user is notified by way of icons whether the current focus position is in the macro region or the magnifying glass region. Also, while Japanese Unexamined Patent Application Publication No. 2003-241069 and Japanese Unexamined Patent Application Publication No. 2005-260792 disclose arrangements wherein a warning is displayed regarding whether the mode will be a normal photography mode or macro photography mode based on measured distance information, issuing such a warning can often lead to missing a photo opportunity.
Also, with compact cameras with no distance measurement sensors or the like, image processing AF is independently used, so distance measurement has to be found out from the focusing lens position when monitoring AF or scanning AF is performed and focus is achieved. Scanning AF operations build on so-called auto-macro operations where the mode automatically makes transition to the macro mode upon detection that the subject is at a close position (macro region). Accordingly, there is no focus limit for each region as with the above-mentioned Japanese Unexamined Patent Application Publication No. 2003-241069 and Japanese Unexamined Patent Application Publication No. 2005-260792, so poor photos are seldom obtained.
Apparatuses provided with such auto-macro functions often calculate the current position from monitoring AF information before half-pressing the release button and make a display regarding whether or not the subject is in a macro region (i.e., displaying a tulip icon) based on that information. However, such icon display processing is primarily based on focus information from during monitoring AF, and may result in trouble such as, in the event of the user changing the angle by panning, tilting, zooming, or the like, just before the time of shooting, the monitoring AF requires time to catch up, resulting in inappropriate icons, or no icon being displayed even though the focus position is in the macro region or magnifying glass region.
Also, there are cameras which perform control to emit AF illuminator for shooting in the event that sufficient light is not available. However, many of such cameras are configured to perform photography emitting light of the same intensity regardless of whether the subject is in the macro region or magnifying glass region, or the normal far region, meaning that the light is often excessive when in the macro region or magnifying glass region, and further electric power is excessively consumed.